With the advent of digital processing technology, the technology for mass production of printed matter has changed from being characterised by the material-absorbing and time-consuming operation of printing presses to a more efficient and flexible technology. Long and short runs of printed matter are now produced by high-speed digital printers controlled by computers and interconnected with processing equipment, resulting in a minimum of preparatory work and resetting between production runs. It is most commonly the case that the only resettings and adaptations required between production runs are those which relate to processing equipment connected to the printer. A basic difference between the new digital technology and the old printing press technology is that the whole of each copy of the printed matter, e.g. a book or a folder, is now produced sequentially page by page. The old printing press technology involved the production, sheet by sheet, of a plurality of copies of the same pages, followed by cutting and binding of the sheets, resulting in simultaneous production of a plurality of copies.
One of the advantages of the modern technology as compared with the old printing press technology is that it allows quick resetting from production of one item of printed matter to another and efficient utilisation of the paper (or other material on which printing is done) used in the production process.
However, there are still disadvantages with the new digital production technology. An example is a situation where the requirement is to produce, for example, two different folders or books and the difference is that they have different numbers of pages which are intended to carry print.
With known digital production technology, such a situation is usually dealt with by the printer being so configured that the pages of the two different folders or books are printed parallel with one another along a paper web which runs through the printer. If the number of pages of the two folders or books are different, the amount of paper web surface which carries no print will be directly proportional to the difference in the numbers of pages. Subsequent processing of the printed paper web in the form of cutting, stacking and binding of the two different folders or books will thus lead to scrapping a large amount of unprinted paper.
One way of avoiding this disadvantageous scrapping of unprinted paper is to so configure the printer that the pages of the folders or books are printed on the paper web in such a way that all the pages of a first book or folder are printed across the whole width of the paper web, followed by printing of all the pages of a second book or folder. Depending on the width of the paper web, two or more pages are printed adjacent to one another so that the whole width of the paper web is utilised. If the printed paper web is subsequently run through a folding device before cutting etc., books or folders are thus created in a sequence whereby scrapping of unprinted paper is largely avoided.
As already indicated above, folding devices are therefore a type of processing equipment commonly used in, for example, contexts where folders or books are to be produced in large numbers. A folding device is typically interconnected with a printer which feeds out a continuous web of paper printed with graphic content, and with a cutting device which receives the folded paper web and cuts it in such a way as to result in separate copies of folders or books.
Although the modern technology for mass production of print products has many advantages such as exemplified above, there nevertheless remain a number of disadvantages which afford scope for improvements. The flexibility resulting from sequential mass production also means that the paper web which is provided with print in the printer and runs through a folding device will run at varying speed and will sometimes be stationary. Depending on the amount of time during which it runs slowly or is completely stationary, the paper web will be exposed to a surrounding atmosphere which affects the material of the paper web in such a way that the mechanical tension of the paper web is altered relative to the tension it has when running through the folding device at high speed. This has an adverse effect on the ability of the folding device to create identical folds for every copy of the products being made.